Fluidized bed system and method for preparing porous carbon and silicon-carbon negative electrode materials

Abstract

The fluidized bed system and method for jointly preparing porous carbon and silicon-carbon negative electrode materials provided by the present invention include a porous carbon preparation subsystem for converting a porous carbon precursor into porous carbon in a fluidized state; a functional group removal subsystem for converting oxygen-containing functional groups on the porous carbon into water for removal to obtain porous carbon after functional group removal; a silicon deposition subsystem for depositing silicon inside the porous carbon after functional group removal to obtain silicon-carbon negative electrode materials; and a carbon coating subsystem for carbon coating the surface of the silicon-carbon negative electrode materials. Among them, the porous carbon preparation subsystem is operated at high temperature, and the other subsystems are all operated at medium temperature. The porous carbon carries heat that can be used to remove functional groups and deposit silicon (endothermic reaction), and the gas heat energy is fully utilized, and natural cooling is achieved. Thus, energy saving and carbon emission goals are achieved. It has the characteristics of continuity, simple operation, large output, low cost, and significantly improved process safety.

Description

Technical Field

[0001] The present invention relates to the technical field of systems and methods for preparing electrode materials for electrochemical energy storage, and in particular to a fluidized bed system and method for jointly preparing porous carbon and silicon-carbon negative electrode materials. Background Art

[0002] Lithium-ion batteries are the most rapidly commercialized secondary batteries. They have high energy density and long driving range, making great contributions to the development of green transportation. For a long time, the negative electrode materials of lithium-ion batteries have been graphite materials, which provide an extremely wide voltage platform and safety. Due to the working principle of lithium-ion batteries, the energy provided by the negative electrode always needs to have a certain degree of abundance to ensure that the positive electrode material can achieve maximum efficiency. In this context, with the commercialization and continuous improvement of the performance of ternary positive electrode materials, the negative electrode also needs to be gradually updated. Among the many solutions, silicon-carbon negative electrode materials have attracted much attention due to their high energy density. However, the intercalation energy storage mechanism of silicon and lithium leads to rapid volume expansion, while the migration of lithium leads to significant volume shrinkage. Therefore, it is necessary to coat the surface of silicon-based materials with carbon, both to alleviate the pulverization caused by volume change and to avoid the rapid reaction of silicon with the electrolyte, reduce the first effect, and produce a large amount of gas to affect safety.

[0003] However, the existing production process of carbon coating the surface of silicon-based materials cannot avoid the generation, existence and release of water and oxygen. In the large-scale preparation process, it will lead to rapid heat release, and there is a risk of thermal runaway or even explosion. In addition, the current actual production situation is that the preparation of porous carbon and the preparation of silicon-carbon negative electrodes are mostly carried out separately, and each link is a high-temperature and high-energy operation, resulting in high production costs, which is very unfavorable to market competition. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention provides a fluidized bed system and method for the joint preparation of porous carbon and silicon-carbon negative electrode materials, so as to achieve the safe preparation of carbon-coated silicon-based materials with low energy consumption and low material consumption.

[0005] The specific content of the invention is as follows:

[0006] In a first aspect, the present invention provides a fluidized bed system for the joint preparation of porous carbon and silicon-carbon negative electrode materials, which is used for the preparation of carbon-coated silicon-based materials, and the system comprises a porous carbon preparation subsystem, a functional group removal subsystem, a silicon deposition subsystem and a carbon coating subsystem connected in sequence;

[0007] Wherein, the porous carbon preparation subsystem is used to convert the porous carbon precursor into porous carbon in a fluidized state;

[0008] The functional group removal subsystem is used to convert the oxygen-containing functional groups on the porous carbon into water, and separate the water from the porous carbon to obtain the porous carbon after the functional groups are removed;

[0009] The silicon deposition subsystem is used to deposit silicon into the porous carbon after the functional groups are removed, so as to obtain a silicon-carbon negative electrode material;

[0010] The carbon coating subsystem is used to perform carbon coating on the surface of the silicon-carbon negative electrode material;

[0011] The tail gas outlet of the porous carbon preparation subsystem is connected to the heat exchange gas inlet of the carbon coating subsystem through a pipeline;

[0012] The tail gas outlet of the carbon coating subsystem is connected to the hydrogen inlet of the functional group removal subsystem through a pipeline.

[0013] Optionally, a filter and a back-blowing gas inlet are provided near the gas outlet of the porous carbon preparation subsystem, and the filter is used to intercept solid particles in the tail gas discharged from the porous carbon preparation subsystem;

[0014] The back-blowing gas inlet is fed with N2 or Ar to blow off the solid particles attached to the filter;

[0015] The porous carbon preparation subsystem is also provided with an activation gas inlet, a porous carbon precursor inlet and a porous carbon outlet.

[0016] Optionally, the functional group removal subsystem is provided with a porous carbon inlet, a porous carbon outlet after functional group removal, and a hydrogen outlet;

[0017] The silicon deposition subsystem is provided with a porous carbon inlet after functional groups are removed, a silane substance inlet, a silicon-carbon negative electrode material outlet, and a silane substance cracking tail gas outlet;

[0018] The carbon coating subsystem is provided with a silicon-carbon negative electrode material inlet, a carbon source gas inlet, an exhaust gas outlet and a final product outlet.

[0019] In a second aspect, the present invention provides a method for jointly preparing porous carbon and silicon-carbon negative electrode materials, the method being applicable to a fluidized bed system for jointly preparing porous carbon and silicon-carbon negative electrode materials as described in the first aspect above, the method comprising the following steps:

[0020] The porous carbon preparation subsystem, the functional group removal subsystem, the silicon deposition subsystem and the carbon coating subsystem are sequentially connected to form a complete system, the temperature of the porous carbon preparation subsystem is controlled at 800-950° C., and the preheated porous carbon precursor is loaded into the porous carbon preparation subsystem through the porous carbon precursor inlet;

[0021] Supplying activation gas to the porous carbon preparation subsystem, placing the porous carbon precursor in the bubbling fluidization and turbulent fluidization operation domain, and controlling the activation reaction time to be 2-10 hours to generate porous carbon;

[0022] The porous carbon is transferred to a functional group removal subsystem, and hydrogen is supplied thereto, so that the porous carbon is in a fast fluidized gas-solid countercurrent operation state, and the heat of the porous carbon is used to react the hydrogen with the oxygen-containing functional groups on the porous carbon for 3-20 minutes, thereby removing the oxygen-containing functional groups on the porous carbon and obtaining the porous carbon after the oxygen-containing functional groups are removed;

[0023] The porous carbon after the functional groups are removed is transferred to a silicon deposition subsystem, and a gas containing a silane-like substance is introduced therein, so that the porous carbon after the functional groups are removed is placed in a bubbling fluidization and turbulent fluidization operation domain, and the heat of the porous carbon is used to crack the silane inside the porous carbon after the functional groups are removed, and silicon is deposited inside the porous carbon, and the reaction time is controlled to be 0.5-4h. After reaching a predetermined amount of silicon, a silicon-carbon negative electrode material is obtained;

[0024] The silicon-carbon negative electrode material is transferred to a carbon coating subsystem, and a carbon source gas is introduced therein, so that the silicon-carbon negative electrode material is in a bubbling fluidization and turbulent fluidization operation domain, and the carbon source is cracked by controlling the reaction temperature and coated on the surface of the silicon-carbon negative electrode material to obtain a final product;

[0025] The tail gas generated by the cracking of the carbon source is introduced into the functional group removal subsystem through the tail gas outlet of the carbon coating subsystem to be used as hydrogen supplement.

[0026] Optionally, when the cracking reaction of the carbon source is an endothermic reaction, the method of controlling the reaction temperature is: passing the tail gas generated by the porous carbon preparation subsystem into the carbon coating subsystem through the tail gas outlet, and using the heat of the tail gas and the silicon-carbon negative electrode material to control the carbon source cracking temperature to 500-750°C;

[0027] When the cracking reaction of the carbon source is an exothermic reaction, the carbon source cracking temperature is controlled to be 400-750° C. by adjusting the amount of carbon source introduced.

[0028] Optionally, the method for controlling the amount of the gas containing silane substances introduced into the silicon deposition subsystem is: by detecting the concentration of the silane substances in the gas discharged from the tail gas outlet of the silane substance cracking, adjusting the amount of the gas containing silane substances introduced, and controlling the concentration to be no higher than 0.05%;

[0029] The control method of the silicon loading amount is: by detecting the pressure drop change of the bed layer of the silicon deposition subsystem, judging whether the predetermined silicon loading amount is reached.

[0030] Optionally, the specific surface area of ​​the porous carbon is 1500-2700m 2 / g, the mesoporosity is 20-75%, the pore volume is 0.8-1.3ml / g, and in the carbon skeleton of the porous carbon, SP 2 Hybridized carbon accounts for 50-70%, and the rest is Sp 3 Hybridized carbon.

[0031] Optionally, the activation gas consists of a mixture of H2O and CO2 in any proportion;

[0032] The porous carbon precursor is a biomass carbon raw material or a polymer carbon raw material, wherein the biomass carbon raw material includes coconut shell and / or starch carbonization product;

[0033] The polymer carbon raw materials include phenolic resin carbonization products and polyacrylonitrile fiber pre-oxidation products.

[0034] Optionally, the oxygen content in the porous carbon after the functional groups are removed is 0.05%-0.001%;

[0035] The carbon source is a combination of one or more of C2-C5 alkanes, alkenes and alkynes.

[0036] Optionally, the gas containing silane substances is a mixed gas of silane substances and hydrogen, or silane substances and argon, wherein the concentration of the silane substances is 5%-95%;

[0037] The silane substance is a combination of one or more of monosilane, disilane and trisilane.

[0038] Optionally, in the silicon-carbon negative electrode material, the mass of silicon is 50-70%.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] The present invention provides a fluidized bed system for preparing porous carbon and silicon-carbon negative electrode materials in combination, which is used for preparing carbon-coated silicon-based materials. The system includes a porous carbon preparation subsystem for converting a porous carbon precursor into porous carbon in a fluidized state; a functional group removal subsystem for converting oxygen-containing functional groups on the porous carbon into water, and separating water from the porous carbon to obtain porous carbon after the functional groups are removed; a silicon deposition subsystem for depositing silicon into the porous carbon after the functional groups are removed to obtain silicon-carbon negative electrode materials; and a carbon coating subsystem for carbon coating the surface of the silicon-carbon negative electrode materials. The porous carbon prepared by the fluidized bed of the present invention has a high consistency in specific surface area and pore size, which provides a basis for the subsequent preparation of highly consistent silicon-carbon negative electrode materials, thereby saving the later separation cost and improving the performance of battery devices using silicon-carbon negative electrode materials. Moreover, since the porous carbon preparation subsystem (the former) performs high-temperature operations for preparing porous carbon, and the other subsystems (the latter) all operate at medium temperatures, during the circulation of the porous carbon in the latter, the corresponding reaction process can be achieved only by relying on the heat energy it carries (considering natural cooling), thereby achieving the goals of energy saving and carbon emissions.

[0041] The present invention also provides a method for preparing carbon-coated silicon-based materials by combining porous carbon and silicon-carbon negative electrode materials. Before depositing silicon in porous carbon, the method first uses hydrogen to convert oxygen-containing functional groups on porous carbon into water vapor and is carried away from porous carbon by hydrogen, thereby avoiding the problem of water and oxygen generation when oxygen-containing functional groups come into contact with silane during the process of depositing silicon in porous carbon, and silane is ignited when it meets water and oxygen. At the same time, the presence of oxygen-containing functional groups during the cracking of carbon sources (hydrocarbon substances) is also eliminated, resulting in the danger of a large amount of adsorption heat generated during the cracking of hydrocarbons for carbon coating (there is a hidden danger of implosion), thereby greatly improving the safety of silane cracking and subsequent carbon coating. Furthermore, the present invention uses the tail gas (mainly hydrogen) generated by the cracking of the carbon source in the carbon coating subsystem as an activation gas for removing oxygen-containing functional groups on porous carbon in the functional group removal subsystem, thereby effectively reducing material consumption.

[0042] In addition, in the method for preparing carbon-coated silicon-based materials provided by the present invention, by controlling the carbon source to be nearly completely cracked, the carbon source is saved, the purity of hydrogen in the tail gas is ensured, and the effective recycling of secondary products is achieved. At the same time, it can also avoid the active carbon source from being recycled in the step of removing functional groups and deposited on the porous carbon surface, thereby producing a pore blocking effect and reducing the subsequent silicon deposition amount. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 The schematic diagram of the structure of the fluidized bed system for preparing the porous carbon and silicon-carbon negative electrode materials provided in the embodiment of the present invention is shown;

[0045] Figure 2 The flowchart of the preparation of the porous carbon and silicon-carbon negative electrode materials provided in the embodiment of the present invention is shown.

[0046] Description of reference numerals:

[0047] 1-porous carbon preparation subsystem; 2-functional group removal subsystem; 3-silicon deposition subsystem; 4-carbon coating subsystem; 5-porous carbon precursor inlet; 6-activation gas inlet; 7-backblowing gas inlet; 8-exhaust gas outlet; 9-porous carbon outlet; 10-porous carbon inlet; 11-hydrogen inlet; 12-hydrogen outlet; 13-porous carbon outlet; 14-porous carbon inlet; 15-silane substance inlet; 16-silane substance cracking exhaust gas outlet; 17-silicon carbon negative electrode material outlet; 18-silicon carbon negative electrode material inlet; 19-carbon source gas inlet; 20-exhaust gas outlet; 21-heat exchange gas inlet; 22-heat exchange gas outlet; 23-final product outlet. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the present invention and its application or use. Based on the embodiments of the present invention, any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work belong to the scope of protection of the present invention.

[0049] In the embodiment, no specific experimental steps or conditions are indicated, and the operation or conditions of the conventional experimental steps described in the prior art in this field can be carried out. The reagents used and other instruments that do not indicate the manufacturer are conventional reagent products that can be obtained commercially. In addition, the accompanying drawings are only schematic diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0050] Technologies, methods, and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the description of the present invention.

[0051] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0052] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0053] Before describing in detail the fluidized bed system and method for preparing the porous carbon and silicon-carbon negative electrode material provided by the present invention, it is necessary to describe the related technologies as follows:

[0054] The existing route for preparing silicon-based materials by first preparing silicon particles and then coating them with a carbon layer for carbon coating still faces the problem of pulverization of electrode materials after long-term use. A more ideal solution is to decompose silane and the like, deposit them inside the porous carbon, and then coat the outside with a carbon layer. As we all know, porous carbon is mainly obtained by carbonization and activation of fossil raw materials (such as phenolic resin, etc.) and biomass raw materials (such as coconut shells, etc.). Whether it is activated by steam, CO2 or alkali, a large number of oxygen-containing functional groups will be generated on the surface of porous carbon. When the oxygen-containing functional groups come into contact with silane, water and oxygen will be generated and released. In the preparation process of large batches, it will lead to rapid heat release and even the risk of explosion. Similarly, if oxygen-containing functional groups exist, when hydrocarbon cracking is used to coat the carbon on the surface, a large amount of adsorption heat will still be released, resulting in thermal runaway of the process.

[0055] In addition, the current actual production situation is that the preparation of porous carbon and the preparation of silicon-carbon negative electrodes are mostly carried out separately. During the production, packaging, transfer and transportation of porous carbon, the surface of porous carbon will inevitably be exposed to water or air, and the end capping of the surface structure contains a large amount of oxygen, which will cause great safety hazards in the subsequent silanization or carbon coating process. In addition, the manufacture of porous carbon, defunctionalization, and each link of silanization or carbon coating are high-temperature and high-energy operations. If each link is carried out independently, each link needs to heat up to react, and each link needs to cool down to preserve the intermediate product. The high-level thermal energy in the process has not been fully and reasonably utilized, resulting in high energy consumption and high production costs, which is very unfavorable to market competition. At the same time, it greatly increases the carbon emissions of the process.

[0056] In order to solve the above technical drawbacks, the present invention hopes to provide a fluidized bed system and method for the joint preparation of porous carbon and silicon-carbon negative electrode materials, through the joint preparation of porous carbon and silicon-carbon negative electrode materials, to achieve controlled removal of functional groups, controlled carbon coating, and recycling of the product (hydrogen), as well as cascade utilization of thermal energy, to ensure the safe preparation of carbon-coated silicon-based materials with low energy consumption and low material consumption. The specific implementation content is as follows:

[0057] In a first aspect, the present invention provides a fluidized bed system for preparing porous carbon and silicon-carbon negative electrode materials, which is used for preparing carbon-coated silicon-based materials. Figure 1 The schematic diagram of the structure of the fluidized bed system for preparing the porous carbon and silicon-carbon negative electrode materials provided in the embodiment of the present invention is shown. Figure 1 As shown, the system includes a porous carbon preparation subsystem 1, a functional group removal subsystem 2, a silicon deposition subsystem 3 and a carbon coating subsystem 4 which are connected in sequence; wherein the porous carbon preparation subsystem 1 is used to convert a porous carbon precursor into porous carbon under a fluidized state; the functional group removal subsystem 2 is used to convert the oxygen-containing functional groups on the porous carbon into water, and separate the water from the porous carbon to obtain the porous carbon after the functional groups are removed; the silicon deposition subsystem 3 is used to deposit silicon into the interior of the porous carbon after the functional groups are removed to obtain a silicon-carbon negative electrode material; the carbon coating subsystem 4 is used to perform carbon coating on the surface of the silicon-carbon negative electrode material; the exhaust gas outlet of the porous carbon preparation subsystem 1 is connected to the carbon coating subsystem 4 through a pipeline; the exhaust gas outlet of the carbon coating subsystem 4 is connected to the hydrogen inlet of the functional group removal subsystem 2 through a pipeline.

[0058] In specific implementation, the flow chart of preparing carbon-coated silicon-based materials using the fluidized bed system provided by the present invention for preparing porous carbon and silicon-carbon negative electrode materials is shown in Figure 2 As shown, the specific steps include:

[0059] S1, connecting the porous carbon preparation subsystem 1, the functional group removal subsystem 2, the silicon deposition subsystem 3 and the carbon coating subsystem 4 in sequence to form a complete system, controlling the temperature of the porous carbon preparation subsystem 1 at 800-950°C, and loading the preheated porous carbon precursor into the porous carbon preparation subsystem 1 through the porous carbon precursor inlet;

[0060] S2, supplying activation gas to the porous carbon preparation subsystem 1, so that the porous carbon precursor is in the bubbling fluidization and turbulent fluidization operation domain, and controlling the activation reaction time to be 2-10 hours to generate porous carbon;

[0061] S3, transferring the porous carbon to the functional group removal subsystem 2, and supplying hydrogen thereto, so that the porous carbon is in a fast fluidized gas-solid countercurrent operation state, and using the heat of the porous carbon itself to react the hydrogen with the oxygen-containing functional groups on the porous carbon for 3-20 minutes, thereby removing the oxygen-containing functional groups on the porous carbon and obtaining the porous carbon after the oxygen-containing functional groups are removed;

[0062] S4, transferring the porous carbon after functional group removal to the silicon deposition subsystem 3, and introducing a gas containing silane substances therein, so that the porous carbon after functional group removal is in the bubbling fluidization and turbulent fluidization operation domain, and utilizing the heat of the porous carbon itself to decompose the silane inside the porous carbon after functional group removal, and depositing silicon inside the porous carbon, the reaction time is controlled to be 0.5-4h, and after reaching a predetermined amount of silicon, a silicon-carbon negative electrode material is obtained;

[0063] S5, transferring the silicon-carbon negative electrode material to the carbon coating subsystem 4, and introducing the carbon source gas thereinto, so that the silicon-carbon negative electrode material is in the bubbling fluidization and turbulent fluidization operation domain, and by controlling the reaction temperature, the carbon source is cracked and coated on the surface of the silicon-carbon negative electrode material to obtain the final product;

[0064] The tail gas generated by the cracking of the carbon source is introduced into the functional group removal subsystem 2 through the tail gas outlet of the carbon gas coating subsystem 4 to be used as a supplement of hydrogen.

[0065] See below Figure 1 The schematic diagram of the system structure shows a detailed description of the preparation process of the carbon-coated silicon-based material. First, the porous carbon precursor after preheating (500-700°C) is loaded into the porous carbon preparation subsystem 1 through the porous carbon precursor inlet 5. Then, the activation gas (a mixture of H2O and CO2 in any proportion) is supplied to the porous carbon preparation subsystem 1 from the activation gas inlet 6 to fluidize the porous carbon precursor (the gas velocity is controlled to be 0.01-0.15m / s). The temperature of the porous carbon preparation subsystem 1 is controlled at 800-950°C, and the activation reaction time of the activation gas on the porous carbon precursor is controlled to be 2-10 hours, so that the porous carbon precursor is converted into porous carbon.

[0066] Continue to see Figure 1 A filter (not shown in the figure) is arranged on the top of the porous carbon preparation subsystem 1. The exhaust gas after the activation reaction will carry some small-particle porous carbon. Before the exhaust gas leaves the porous carbon preparation subsystem 1, it is first processed by the filter, and then leaves the porous carbon preparation subsystem 1 through the exhaust gas outlet 8 to intercept the small-particle porous carbon therein. The back-blowing gas (N2 or Ar) is introduced into the back-blowing gas inlet 7 to blow off the carbon products attached to the filter and return to the porous carbon preparation subsystem 1 to reduce carbon emissions in the exhaust gas.

[0067] Continue to see Figure 1 The porous carbon is taken out of the porous carbon preparation subsystem 1 through the porous carbon outlet 9, and then enters the functional group removal subsystem 2 through the porous carbon inlet 10. Hydrogen is introduced from the hydrogen inlet 11, and the heat carried by the porous carbon is used to react with the oxygen-containing functional groups on the porous carbon at the corresponding temperature (700-900° C.) for 3-20 minutes to generate water, which is carried by the hydrogen and goes out of the functional group removal subsystem 2 through the hydrogen outlet 12.

[0068] Continue to see Figure 1 , the porous carbon after functional group removal exits the functional group removal subsystem 2 from the porous carbon outlet 13 after functional group removal, and then enters the silicon deposition subsystem 3 through the porous carbon inlet 14 after functional group removal. A gas containing silane substances is introduced from the silane substance inlet 15, and the heat carried by the porous carbon after natural cooling is utilized. At the corresponding temperature (400°C to 850°C), the silane substances are cracked inside the porous carbon, and the reaction time is controlled to be 0.5-4 hours. Silicon is deposited inside the porous carbon to obtain a silicon-carbon negative electrode material. In the embodiment of the present invention, the concentration of silane substances in the tail gas at the tail gas outlet 16 of the silane substance cracking is generally not higher than 0.05%, so as to control the silane feed amount so as to make the silane nearly completely converted. Further, by detecting the pressure drop change of the bed of the silicon deposition subsystem 3, it is judged whether the predetermined amount of silicon is reached to control the reaction end point. The tail gas generated by the cracking of the silane substances exits the silicon deposition subsystem 3 from the tail gas outlet 16 of the silane substance cracking.

[0069] Continue to see Figure 1After reaching the predetermined amount of silicon, the obtained silicon-carbon negative electrode material is removed from the silicon deposition subsystem 3 through the silicon-carbon negative electrode material outlet 17, and enters the carbon coating subsystem 4 through the silicon-carbon negative electrode material inlet 18. A carbon source is introduced into the carbon coating subsystem 4 from the carbon source gas inlet 19 for 5-60 minutes, the carbon source is decomposed and coated on the surface of the silicon-carbon negative electrode material, and the obtained carbon-coated silicon-based material is discharged through the final product outlet 23. In specific implementation, the temperature regulation method of the carbon coating subsystem 4 is determined by the type of carbon source cracking reaction. If the carbon source cracking reaction is an exothermic process, the process temperature (400-750°C) is controlled by the amount of carbon source introduced; the tail gas generated by the carbon source cracking is discharged through the tail gas outlet 20; if the carbon source cracking reaction is an endothermic reaction, the tail gas generated by the porous carbon preparation subsystem 1 is used as a heat exchange gas and introduced into the carbon coating subsystem 4 through the heat exchange gas inlet 21, and the heat carried by the heat exchange gas and the silicon-carbon negative electrode material (considering natural cooling) is used to control the carbon source cracking temperature (500-750°C). The heat exchange gas finally exits the carbon coating subsystem 4 through the heat exchange gas outlet 22. In specific implementation, the amount of carbon source added is controlled so that the carbon source at the outlet of the carbon coating subsystem 4 is nearly completely converted.

[0070] Continue to see Figure 1 The tail gas (mainly hydrogen and a small amount of methane) generated by the cracking of the carbon source leaves the carbon coating subsystem 4 through the tail gas outlet 20. Then it circulates to the functional group removal subsystem 2 through the hydrogen inlet 11 to remove the oxygen-containing functional groups on the porous carbon, thereby realizing the effective utilization of the secondary products.

[0071] Before depositing silicon in porous carbon, the present invention first converts the oxygen-containing functional groups on the porous carbon into water vapor with the help of hydrogen and is carried away from the porous carbon by hydrogen, thereby avoiding the problem of water and oxygen generation when the oxygen-containing functional groups come into contact with silane during the process of depositing silicon in porous carbon, and silane is in danger of catching fire when it meets water and oxygen. At the same time, the presence of oxygen-containing functional groups during the cracking of carbon sources (hydrocarbon substances) is also eliminated, resulting in the danger of a large amount of adsorption heat generated during the cracking of hydrocarbons for carbon coating (there is a hidden danger of implosion), which greatly improves the safety of silane cracking and subsequent carbon coating. Furthermore, the present invention uses the tail gas (mainly hydrogen) generated by the cracking of the carbon source in the carbon coating subsystem as an activated gas for removing the oxygen-containing functional groups on the porous carbon in the functional group removal subsystem, effectively reducing material consumption. In addition, the present invention also controls the carbon source to be nearly completely cracked, which not only saves the carbon source, but also ensures the purity of the hydrogen in the tail gas, and realizes the effective reuse of secondary products. At the same time, it is also possible to avoid the active carbon source from being recycled into the step of removing functional groups and deposited on the porous carbon surface, thereby producing a pore-blocking effect and reducing the subsequent silicon deposition amount. The most important point is that the present invention takes into account that the porous carbon preparation subsystem 1 (the former) performs high-temperature operation for the preparation of porous carbon, and the remaining subsystems (the latter) are all medium-temperature operations. Therefore, during the circulation of porous carbon in the latter, the corresponding reaction process can be achieved only by the heat energy it carries (considering natural cooling), thereby achieving the goals of energy saving and carbon emissions.

[0072] In some embodiments, the porous carbon precursor is a biomass carbon raw material or a polymer carbon raw material, wherein the biomass carbon raw material includes carbonized products of coconut shell and / or starch; the polymer carbon raw material includes carbonized products of phenolic resin and pre-oxidized products of polyacrylonitrile fiber. The specific surface area of ​​the porous carbon prepared by the system provided in the embodiment of the present invention is 1500-2700m 2 / g, the mesoporosity is 20-75%, the pore volume is 0.8-1.3ml / g, and the carbon skeleton of porous carbon has SP 2 Hybridized carbon accounts for 50-70%, and the rest is Sp 3 Hybridized carbon.

[0073] In some embodiments, the oxygen content in the porous carbon after the functional groups are removed is 0.05%-0.001%;

[0074] In some embodiments, the carbon source is a combination of one or more of C2-C5 alkanes, alkenes, and alkynes.

[0075] In some embodiments, the gas containing silane substances is a mixed gas of silane substances and hydrogen, or silane substances and argon, wherein the concentration of the silane substances is 5%-95%; the silane substances are a combination of one or more of monosilane, disilane and trisilane.

[0076] In some embodiments, the mass of silicon in the silicon-carbon negative electrode material is 50-70%.

[0077] In order to enable those skilled in the art to more clearly understand the present invention, the fluidized bed system and method for jointly preparing the porous carbon and silicon-carbon negative electrode materials described in the present invention are now described in detail through the following examples.

[0078] Example 1

[0079] like Figure 1 As shown in the connection relationship, the porous carbon preparation subsystem 1, the functional group removal subsystem 2, the silicon deposition subsystem 3 and the carbon coating subsystem 4 are sequentially connected to form a complete system.

[0080] The porous carbon precursor (biomass raw material, such as the product obtained by carbonizing coconut shell) is loaded into the subsystem 1 through the porous carbon precursor inlet 5. The activation gas (H2O) is supplied to the subsystem 1 from the back-blowing gas inlet 7 to put the porous carbon precursor in a fluidized state (the gas velocity is controlled to be 0.15m / s, and the subsystem 1 is in the turbulent fluidization operation domain). The temperature of the subsystem 1 is raised to 950°C. The activation reaction time is controlled to be 2 hours to generate porous carbon (with a specific surface area of ​​1500m 2 / g. The mesoporosity is 20%. The pore volume is 0.8ml / g. The SP 2 Hybridized carbon accounts for 50% and the rest is Sp 3 hybrid carbon).

[0081] After activation, the tail gas carries some small-size solids and reaches the top of subsystem 1 (with a filter inside), and the backwash gas (N2) is introduced through the backwash gas inlet 7 to blow off the carbon products attached to the filter and return to subsystem 1. After passing through the filter, the tail gas leaves subsystem 1 through the tail gas outlet 8.

[0082] The porous carbon product exits the subsystem 1 through the porous carbon outlet 9, and then enters the subsystem 2 through the porous carbon inlet 10 (the particles in the subsystem 2 are in a fast fluidized gas-solid countercurrent operation state). Hydrogen is introduced from the hydrogen inlet 11, and the heat carried by the porous carbon is used to react with the oxygen-containing functional groups on the porous carbon at the corresponding temperature (900° C.) for 3 minutes to generate water, which is carried by the hydrogen and exits the subsystem 2 through the hydrogen outlet 12.

[0083] The porous carbon (oxygen content is 0.02%) after the functional groups are removed leaves subsystem 2 from the porous carbon outlet 13, and then enters subsystem 3 through the porous carbon inlet 14 (the particles of subsystem 3 are in the turbulent fluidization operation domain). Silane substances (5% monosilane, 95% H2) are introduced from the silane substance inlet 15. The heat carried by the porous carbon is used to crack the silane inside the porous carbon at the corresponding temperature (850°C). The reaction time is controlled to be 0.5 hours, and silicon is deposited inside the porous carbon. By detecting the concentration of the exhaust gas, the silane feed amount is controlled to achieve near-complete conversion of the silane. By detecting the change in the pressure drop of the bed, the amount of silicon is fed back to control the reaction endpoint. The exhaust gas leaves subsystem 3 from the silane substance cracking exhaust gas outlet 16.

[0084] After reaching the predetermined amount of silicon, the obtained silicon-carbon negative electrode material (the mass of silicon is 50%, and the silicon is deposited inside the porous carbon) is removed from subsystem 3 through the outlet 17 of the silicon-carbon negative electrode material. And enter subsystem 4 through the inlet 18 of the silicon-carbon negative electrode material (the particles in subsystem 4 are in the bubbling fluidization operation domain). The carbon source (acetylene) is introduced into subsystem 4 from the carbon source gas inlet 19. The heat and corresponding temperature on the silicon-carbon negative electrode material are used to decompose the carbon source, and within 5 minutes, carbon coating is achieved on the surface of the silicon-carbon negative electrode material to obtain the final product (carbon-coated silicon-carbon negative electrode material). Acetylene cracking is an exothermic reaction, and the process temperature is controlled at 400°C by the amount of carbon source introduced.

[0085] The amount of carbon source added is controlled so that the carbon source at the outlet of subsystem 4 is nearly completely converted. The tail gas (mainly hydrogen and a small amount of methane) generated by the cracking of the carbon source leaves subsystem 4 through tail gas outlet 20. It is then circulated to the hydrogen inlet 11 of subsystem 2 and used as a supplement to the hydrogen in subsystem 2.

[0086] Example 2

[0087] like Figure 1 As shown in the connection relationship, the porous carbon preparation subsystem 1, the functional group removal subsystem 2, the silicon deposition subsystem 3 and the carbon coating subsystem 4 are sequentially connected to form a complete system.

[0088] The porous carbon precursor (microporous carbon raw material) is loaded into the subsystem 1 through the porous carbon precursor inlet 5. The activation gas (CO2) is supplied to the subsystem 1 from the backflush gas inlet 7 to fluidize the porous carbon precursor (the gas velocity is controlled to be 0.01 m / s, and the subsystem 1 is in the bubbling fluidization operation domain). The temperature of the subsystem 1 is raised to 900°C. The activation reaction time is controlled to be 10 hours to generate porous carbon (specific surface area of ​​2700 m 2 / g. The mesoporosity is 75%. The pore volume is 1.3ml / g. The SP 2 Hybridized carbon accounts for 70% and the rest is Sp 3 hybrid carbon).

[0089] After activation, the tail gas carries some small-size solids and reaches the top of subsystem 1 (with a filter inside), and the backwash gas (Ar) is introduced through inlet 7 to blow off the carbon products attached to the filter and return to subsystem 1. After passing through the filter, the tail gas leaves subsystem 1 through tail gas outlet 8.

[0090] The porous carbon product exits the subsystem 1 through the porous carbon outlet 9, and then enters the subsystem 2 through the porous carbon inlet 10 (the particles in the subsystem 2 are in a fast fluidized gas-solid countercurrent operation state). Hydrogen is introduced from the hydrogen inlet 11, and the heat carried by the porous carbon is used to react with the oxygen-containing functional groups on the porous carbon at the corresponding temperature (800° C.) for 20 minutes to generate water, which is carried by the hydrogen and exits the subsystem 2 through the hydrogen outlet 12.

[0091] The porous carbon (oxygen content is 0.002%) after the functional groups are removed leaves subsystem 2 from porous carbon outlet 13, and then enters subsystem 3 through porous carbon inlet 14. Silane substances (50% monosilane, 50% H2) are introduced from silane substance inlet 15, and the heat carried by the porous carbon is used to crack the silane inside the porous carbon at the corresponding temperature (700°C). The reaction time is controlled to be 4 hours, and silicon is deposited inside the porous carbon. By detecting the concentration of the tail gas, the silane feed amount is controlled to achieve near-complete conversion of the silane. By detecting the change in the pressure drop of the bed, the amount of silicon is fed back to control the reaction endpoint. The tail gas leaves subsystem 3 from the tail gas outlet 16 of the cracking of the silane substance.

[0092] After reaching the predetermined amount of silicon, the obtained silicon-carbon negative electrode material (the mass of silicon is 70%, and the silicon is deposited inside the porous carbon) is removed from subsystem 3 through the outlet 17 of the silicon-carbon negative electrode material (the particles in subsystem 3 are in the bubbling fluidization operation domain). And enter subsystem 4 through the inlet 18 of the silicon-carbon negative electrode material (the particles in subsystem 4 are in the turbulent fluidization operation domain). A carbon source (50% ethylene, 20% propylene, 10% butane, 20 pentane) is introduced into subsystem 4 from the carbon source gas inlet 19. The heat and corresponding temperature on the silicon-carbon negative electrode material are used to decompose the carbon source, and carbon coating is achieved on the surface of the silicon-carbon negative electrode material within 60 minutes to obtain the final product (carbon-coated silicon-carbon negative electrode material).

[0093] The carbon source cracking is an endothermic reaction, so the tail gas at the outlet of subsystem 1 is introduced into the heat exchange layer of the subsystem through the inlet 21 to ensure the carbon source cracking temperature (750° C.), and then exits from the outlet 22 .

[0094] The amount of carbon source added is controlled so that the carbon source at the outlet of subsystem 4 is nearly completely converted. The tail gas (mainly hydrogen and a small amount of methane) generated by the cracking of the carbon source leaves subsystem 4 through tail gas outlet 20. It is then circulated to the hydrogen inlet 11 of subsystem 2 and used as a supplement to the hydrogen in subsystem 2.

[0095] Example 3

[0096] like Figure 1 As shown in the connection relationship, the porous carbon preparation subsystem 1, the functional group removal subsystem 2, the silicon deposition subsystem 3 and the carbon coating subsystem 4 are sequentially connected to form a complete system.

[0097] The porous carbon precursor (polymer raw material, such as the product obtained by carbonizing phenolic resin) is loaded into the subsystem 1 through the porous carbon precursor inlet 5. The activation gas (50% H2O, 50% CO2) is supplied to the subsystem 1 from the backflush gas inlet 7 to fluidize the porous carbon precursor (the gas velocity is controlled at 0.08 m / s, and the subsystem 1 is in the turbulent fluidization operation domain). The temperature of the subsystem 1 is raised to 800°C. The activation reaction time is controlled to 7 hours to generate porous carbon (specific surface area of ​​2000 m 2 / g. The mesoporosity is 45%. The pore volume is 1.12ml / g. The SP 2 Hybridized carbon accounts for 60% and the rest is Sp 3 hybrid carbon).

[0098] After activation, the tail gas carries some small-size solids and reaches the top of subsystem 1 (with a filter inside), and the back-blowing gas (N2) is introduced through inlet 7 to blow off the carbon products attached to the filter and return to subsystem 1. After passing through the filter, the tail gas leaves subsystem 1 through tail gas outlet 8.

[0099] The porous carbon product exits the subsystem 1 through the porous carbon outlet 9, and then enters the subsystem 2 through the porous carbon inlet 10 (the particles in the subsystem 2 are in a fast fluidized gas-solid countercurrent operation state). Hydrogen is introduced from the hydrogen inlet 11, and the heat carried by the porous carbon is used to react with the oxygen-containing functional groups on the porous carbon at the corresponding temperature (700° C.) for 15 minutes to generate water, which is carried by the hydrogen and exits the subsystem 2 through the hydrogen outlet 12.

[0100] The porous carbon (oxygen content is 0.001%) after the functional groups are removed leaves the subsystem 2 from the porous carbon outlet 13, and then enters the subsystem 3 through the porous carbon inlet 14. Silane substances (25% monosilane, 65% disilane, 10% H2) are introduced from the silane substance inlet 15. The heat carried by the porous carbon is used to crack the silane inside the porous carbon at the corresponding temperature (400°C). The reaction time is controlled to be 4 hours, and silicon is deposited inside the porous carbon. By detecting the concentration of the tail gas, the silane feed amount is controlled to achieve near-complete conversion of the silane. By detecting the change in the pressure drop of the bed, the amount of silicon is fed back to control the reaction endpoint. The tail gas leaves the subsystem 3 from the tail gas outlet 16 for cracking of the silane substance.

[0101] After reaching the predetermined amount of silicon, the obtained silicon-carbon negative electrode material (silicon mass is 55%, and silicon is deposited inside the porous carbon) is removed from subsystem 3 through the outlet 17 of the silicon-carbon negative electrode material (the particles in subsystem 3 are in the turbulent fluidization operation domain). And enter subsystem 4 through the inlet 18 of the silicon-carbon negative electrode material (the particles in subsystem 4 are in the bubbling fluidization operation domain). A carbon source (65% propyne, 3% acetylene, 32% propylene) is introduced into subsystem 4 from the carbon source gas inlet 19. The heat and corresponding temperature on the silicon-carbon negative electrode material are used to decompose the carbon source, and carbon coating is achieved on the surface of the silicon-carbon negative electrode material within 30 minutes to obtain the final product (carbon-coated silicon-carbon negative electrode material).

[0102] The cracking of the carbon source is an exothermic reaction, and the process temperature (750°C) is controlled by the amount of carbon source introduced.

[0103] The amount of carbon source added is controlled so that the carbon source at the outlet of subsystem 4 is nearly completely converted. The tail gas (mainly hydrogen and a small amount of methane) generated by the cracking of the carbon source leaves subsystem 4 through tail gas outlet 20. It is then circulated to the hydrogen inlet 11 of subsystem 2 and used as a supplement to the hydrogen in subsystem 2.

[0104] Example 4

[0105] like Figure 1 As shown in the connection relationship, the porous carbon preparation subsystem 1, the functional group removal subsystem 2, the silicon deposition subsystem 3 and the carbon coating subsystem 4 are sequentially connected to form a complete system.

[0106] The porous carbon precursor (polymer raw material, such as the product obtained by pre-oxidation of polyacrylonitrile fiber) is loaded into the subsystem 1 through the porous carbon precursor inlet 5. The activation gas (CO2) is supplied to the subsystem 1 from the backflush gas inlet 7 to put the porous carbon precursor in a fluidized state (the gas velocity is controlled to be 0.05m / s, and the subsystem 1 is in the turbulent fluidization operation domain). The temperature of the subsystem 1 is raised to 920°C. The activation reaction time is controlled to be 5 hours to generate porous carbon (with a specific surface area of ​​1800m 2 / g. The mesoporosity is 60%. The pore volume is 0.9ml / g. The SP 2 Hybridized carbon accounts for 54%, and the rest is Sp 3 hybrid carbon).

[0107] After activation, the tail gas carries some small-size solids and reaches the top of subsystem 1 (with a filter inside), and the backwash gas (Ar) is introduced through inlet 7 to blow off the carbon products attached to the filter and return to subsystem 1. After passing through the filter, the tail gas leaves subsystem 1 through tail gas outlet 8.

[0108] The porous carbon product exits the subsystem 1 through the porous carbon outlet 9, and then enters the subsystem 2 through the porous carbon inlet 10 (the particles in the subsystem 2 are in a fast fluidized gas-solid countercurrent operation state). Hydrogen is introduced from the hydrogen inlet 11, and the heat carried by the porous carbon is used to react with the oxygen-containing functional groups on the porous carbon at the corresponding temperature (820° C.) for 10 minutes to generate water, which is carried by the hydrogen and exits the subsystem 2 through the hydrogen outlet 12.

[0109] The porous carbon (oxygen content is 0.05%) after the functional groups are removed leaves subsystem 2 from the porous carbon outlet 13, and then enters subsystem 3 through the porous carbon inlet 14 (the particles of subsystem 3 are in the turbulent fluidization operation domain). Silane substances (25% monosilane, 10% disilane, 25% trisilane, 40% H2) are introduced from the silane substance inlet 15. The heat carried by the porous carbon is used to crack the silane inside the porous carbon at the corresponding temperature (500°C). The reaction time is controlled to be 2 hours, and silicon is deposited inside the porous carbon. By detecting the concentration of the tail gas, the silane feed amount is controlled to achieve near-complete conversion of the silane. By detecting the change in the pressure drop of the bed, the amount of silicon is fed back to control the reaction endpoint. The tail gas leaves subsystem 3 from the tail gas outlet 16 for cracking of the silane substance.

[0110] After reaching the predetermined amount of silicon, the obtained silicon-carbon negative electrode material (the mass of silicon is 60%, and the silicon is deposited inside the porous carbon) is removed from subsystem 3 through the outlet 17 of the silicon-carbon negative electrode material. And enter subsystem 4 through the inlet 18 of the silicon-carbon negative electrode material (the particles in subsystem 4 are in the turbulent fluidization operation domain). A carbon source (20% ethane, 50% ethylene, 30% acetylene) is introduced into subsystem 4 from the carbon source gas inlet 19. The cracking of the carbon source is an endothermic reaction. The tail gas at the outlet of subsystem 1 is introduced into the heat exchange layer of the subsystem through the inlet 21. The carbon source cracking temperature (500°C) is controlled in conjunction with the heat on the silicon-carbon negative electrode material, and then it is discharged from the outlet 22. Within 20 minutes, the carbon source decomposes and carbon coating is achieved on the surface of the silicon-carbon negative electrode material to obtain the final product (carbon-coated silicon-carbon negative electrode material).

[0111] The amount of carbon source added is controlled so that the carbon source at the outlet of subsystem 4 is nearly completely converted. The tail gas (mainly hydrogen and a small amount of methane) generated by the cracking of the carbon source leaves subsystem 4 through tail gas outlet 20. It is then circulated to the hydrogen inlet 11 of subsystem 2 and used as a supplement to the hydrogen in subsystem 2.

[0112] Example 5

[0113] The porous carbon preparation subsystem 1, the functional group removal subsystem 2, the silicon deposition subsystem 3 and the carbon coating subsystem 4 are connected in the order of 1, 2, 3, 4 to form a complete system.

[0114] The porous carbon precursor (biomass raw material, a product obtained by cross-linking and carbonizing starch) is loaded into the subsystem 1 through the porous carbon precursor inlet 5. The activation gas (40% H2O, 60% CO2) is supplied to the subsystem 1 from the backflush gas inlet 7 to fluidize the porous carbon precursor (the gas velocity is controlled at 0.10 m / s, and the subsystem 1 is in the turbulent fluidization operation domain). The temperature of the subsystem 1 is raised to 820°C. The activation reaction time is controlled to 6.5 hours to generate porous carbon (specific surface area of ​​1900 m 2 / g. The mesoporosity is 50%. The pore volume is 0.92ml / g. The SP 2 Hybridized carbon accounts for 50% and the rest is Sp 3 hybrid carbon).

[0115] After activation, the tail gas carries some small-size solids and reaches the top of subsystem 1 (with a filter inside), and back-blowing gas (50% N2, 50% Ar) is introduced through inlet 7 to blow off the carbon products attached to the filter and return to subsystem 1. After passing through the filter, the tail gas leaves subsystem 1 through tail gas outlet 8.

[0116] The porous carbon product exits the subsystem 1 through the porous carbon outlet 9, and then enters the subsystem 2 through the porous carbon inlet 10 (the particles in the subsystem 2 are in a fast fluidized gas-solid countercurrent operation state). Hydrogen is introduced from the hydrogen inlet 11, and the heat carried by the porous carbon is used to react with the oxygen-containing functional groups on the porous carbon at the corresponding temperature (700° C.) for 20 minutes to generate water, which is carried by the hydrogen and exits the subsystem 2 through the hydrogen outlet 12.

[0117] The porous carbon (oxygen content is 0.025%) after the functional groups are removed leaves subsystem 2 from the porous carbon outlet 13, and then enters subsystem 3 through the porous carbon inlet 14 (the particles of subsystem 3 are in the turbulent fluidization operation domain). Silane substances (5% monosilane, 15% trisilane, 80% H2) are introduced from the silane substance inlet 15. The heat carried by the porous carbon is used to crack the silane inside the porous carbon at the corresponding temperature (400°C). The reaction time is controlled to be 4 hours, and silicon is deposited inside the porous carbon. By detecting the concentration of the tail gas, the silane feed amount is controlled to achieve near-complete conversion of the silane. By detecting the change in the pressure drop of the bed, the amount of silicon is fed back to control the reaction endpoint. The tail gas leaves subsystem 3 from the tail gas outlet 16 of the cracking of the silane substance.

[0118] After reaching the predetermined amount of silicon, the obtained silicon-carbon negative electrode material (silicon mass is 56%, and silicon is deposited inside the porous carbon) is removed from subsystem 3 through the outlet 17 of the silicon-carbon negative electrode material. And enter subsystem 4 through the inlet 18 of the silicon-carbon negative electrode material (the particles in subsystem 4 are in the bubbling fluidization operation domain). The carbon source (ethylene) is introduced into subsystem 4 from the carbon source gas inlet 19. The cracking of the carbon source is an exothermic reaction. The carbon source flow rate is controlled, and the heat on the silicon-carbon negative electrode material is coordinated to control the carbon source cracking temperature (650°C), and then it is discharged from the outlet 22. Within 15 minutes, the carbon source decomposes and carbon coating is achieved on the surface of the silicon-carbon negative electrode material to obtain the final product (carbon-coated silicon-carbon negative electrode material).

[0119] The amount of carbon source added is controlled so that the carbon source at the outlet of subsystem 4 is nearly completely converted. The tail gas (mainly hydrogen and a small amount of methane) generated by the cracking of the carbon source leaves subsystem 4 through tail gas outlet 20. It is then circulated to the hydrogen inlet 11 of subsystem 2 and used as a supplement to the hydrogen in subsystem 2.

[0120] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0121] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily required by the present invention.

[0122] The fluidized bed system and method for jointly preparing the porous carbon and silicon-carbon negative electrode materials provided by the present invention are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technicians in this field, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A fluidized bed system for preparing porous carbon and silicon-carbon negative electrode materials, used for preparing carbon-coated silicon-based materials, characterized in that: The system comprises a porous carbon preparation subsystem, a functional group removal subsystem, a silicon deposition subsystem and a carbon coating subsystem which are connected in sequence; Wherein, the porous carbon preparation subsystem is used to convert the porous carbon precursor into porous carbon in a fluidized state; The functional group removal subsystem is used to convert the oxygen-containing functional groups on the porous carbon into water, and separate the water from the porous carbon to obtain the porous carbon after the functional groups are removed; The silicon deposition subsystem is used to deposit silicon into the porous carbon after the functional groups are removed, so as to obtain a silicon-carbon negative electrode material; The carbon coating subsystem is used to perform carbon coating on the surface of the silicon-carbon negative electrode material; The tail gas outlet of the porous carbon preparation subsystem is connected to the heat exchange gas inlet of the carbon coating subsystem through a pipeline; The tail gas outlet of the carbon coating subsystem is connected to the hydrogen inlet of the functional group removal subsystem through a pipeline.

2. The fluidized bed system for preparing porous carbon and silicon-carbon negative electrode materials according to claim 1, characterized in that: A filter and a back-blowing gas inlet are provided near the gas outlet of the porous carbon preparation subsystem, wherein the filter is used to intercept solid particles in the tail gas discharged from the porous carbon preparation subsystem; The back-blowing gas inlet is fed with N2 or Ar to blow off the solid particles attached to the filter; The porous carbon preparation subsystem is also provided with an activation gas inlet, a porous carbon precursor inlet and a porous carbon outlet.

3. The fluidized bed system for preparing porous carbon and silicon-carbon negative electrode materials according to claim 1, characterized in that: The functional group removal subsystem is provided with a porous carbon inlet, a porous carbon outlet after functional group removal, and a hydrogen outlet; The silicon deposition subsystem is provided with a porous carbon inlet after functional groups are removed, a silane substance inlet, a silicon-carbon negative electrode material outlet, and a silane substance cracking tail gas outlet; The carbon coating subsystem is provided with a silicon-carbon negative electrode material inlet, a carbon source gas inlet, an exhaust gas outlet and a final product outlet.

4. A method for preparing porous carbon and silicon-carbon negative electrode materials, characterized in that: The method is applicable to a fluidized bed system for preparing the porous carbon and silicon-carbon negative electrode materials jointly as described in any one of claims 1 to 3, and the method comprises the following steps: The porous carbon preparation subsystem, the functional group removal subsystem, the silicon deposition subsystem and the carbon coating subsystem are sequentially connected to form a complete system, the temperature of the porous carbon preparation subsystem is controlled at 800-950° C., and the preheated porous carbon precursor is loaded into the porous carbon preparation subsystem through the porous carbon precursor inlet; Supplying activation gas to the porous carbon preparation subsystem, placing the porous carbon precursor in the bubbling fluidization and turbulent fluidization operation domain, and controlling the activation reaction time to be 2-10 hours to generate porous carbon; The porous carbon is transferred to a functional group removal subsystem, and hydrogen is supplied thereto, so that the porous carbon is in a fast fluidized gas-solid countercurrent operation state, and the heat of the porous carbon is used to react the hydrogen with the oxygen-containing functional groups on the porous carbon for 3-20 minutes, thereby removing the oxygen-containing functional groups on the porous carbon and obtaining the porous carbon after the oxygen-containing functional groups are removed; The porous carbon after the functional groups are removed is transferred to a silicon deposition subsystem, and a gas containing a silane-like substance is introduced therein, so that the porous carbon after the functional groups are removed is placed in a bubbling fluidization and turbulent fluidization operation domain, and the heat of the porous carbon is used to crack the silane inside the porous carbon after the functional groups are removed, and silicon is deposited inside the porous carbon, and the reaction time is controlled to be 0.5-4h. After reaching a predetermined amount of silicon, a silicon-carbon negative electrode material is obtained; The silicon-carbon negative electrode material is transferred to a carbon coating subsystem, and a carbon source gas is introduced therein, so that the silicon-carbon negative electrode material is in a bubbling fluidization and turbulent fluidization operation domain, and the carbon source is cracked by controlling the reaction temperature and coated on the surface of the silicon-carbon negative electrode material to obtain a final product; The tail gas generated by the cracking of the carbon source is introduced into the functional group removal subsystem through the tail gas outlet of the carbon coating subsystem to be used as hydrogen supplement.

5. The method for preparing porous carbon and silicon-carbon negative electrode materials according to claim 4, characterized in that: When the cracking reaction of the carbon source is an endothermic reaction, the method of controlling the reaction temperature is: the tail gas generated by the porous carbon preparation subsystem is introduced into the carbon coating subsystem through the tail gas outlet, and the heat of the tail gas and the silicon-carbon negative electrode material is used to control the carbon source cracking temperature to 500-750°C; When the cracking reaction of the carbon source is an exothermic reaction, the carbon source cracking temperature is controlled to be 400-750° C. by adjusting the amount of carbon source introduced.

6. The method for preparing porous carbon and silicon-carbon negative electrode materials according to claim 4, characterized in that: The method for controlling the amount of the gas containing silane substances introduced into the silicon deposition subsystem is as follows: by detecting the concentration of the silane substances in the gas discharged from the tail gas outlet of the silane substance cracking, adjusting the amount of the gas containing silane substances introduced, and controlling the concentration to be no higher than 0.05%; The control method of the silicon loading amount is: by detecting the pressure drop change of the bed layer of the silicon deposition subsystem, judging whether the predetermined silicon loading amount is reached.

7. The method for preparing porous carbon and silicon-carbon negative electrode materials according to claim 4, characterized in that: The specific surface area of ​​the porous carbon is 1500-2700m 2 / g, the mesoporosity is 20-75%, the pore volume is 0.8-1.3ml / g, and in the carbon skeleton of the porous carbon, SP 2 Hybridized carbon accounts for 50-70%, and the rest is Sp 3 Hybridized carbon.

8. The method for preparing porous carbon and silicon-carbon negative electrode materials according to claim 4, characterized in that: The activation gas is composed of H2O and CO2 mixed in any proportion; The porous carbon precursor is a biomass carbon raw material or a polymer carbon raw material, wherein the biomass carbon raw material includes coconut shell and / or starch carbonization product; The polymer carbon raw materials include phenolic resin carbonization products and polyacrylonitrile fiber pre-oxidation products.

9. The method for preparing porous carbon and silicon-carbon negative electrode materials according to claim 4, characterized in that: The oxygen content in the porous carbon after the functional groups are removed is 0.05%-0.001%; The carbon source is a combination of one or more of C2-C5 alkanes, alkenes and alkynes; The gas containing silane substances is a mixed gas of silane substances and hydrogen, or silane substances and argon, wherein the concentration of the silane substances is 5%-95%; The silane substance is a combination of one or more of monosilane, disilane and trisilane.

10. The method for preparing porous carbon and silicon-carbon negative electrode materials according to claim 4, characterized in that: In the silicon-carbon negative electrode material, the mass of silicon is 50-70%.

Images